… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head1 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | #include <ev.h> |
11 | #include <ev.h> |
12 | |
12 | |
13 | ev_io stdin_watcher; |
13 | ev_io stdin_watcher; |
14 | ev_timer timeout_watcher; |
14 | ev_timer timeout_watcher; |
… | |
… | |
65 | You register interest in certain events by registering so-called I<event |
65 | You register interest in certain events by registering so-called I<event |
66 | watchers>, which are relatively small C structures you initialise with the |
66 | watchers>, which are relatively small C structures you initialise with the |
67 | details of the event, and then hand it over to libev by I<starting> the |
67 | details of the event, and then hand it over to libev by I<starting> the |
68 | watcher. |
68 | watcher. |
69 | |
69 | |
70 | =head1 FEATURES |
70 | =head2 FEATURES |
71 | |
71 | |
72 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
72 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
73 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
73 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
74 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
74 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
75 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
75 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
… | |
… | |
82 | |
82 | |
83 | It also is quite fast (see this |
83 | It also is quite fast (see this |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
85 | for example). |
85 | for example). |
86 | |
86 | |
87 | =head1 CONVENTIONS |
87 | =head2 CONVENTIONS |
88 | |
88 | |
89 | Libev is very configurable. In this manual the default configuration will |
89 | Libev is very configurable. In this manual the default configuration will |
90 | be described, which supports multiple event loops. For more info about |
90 | be described, which supports multiple event loops. For more info about |
91 | various configuration options please have a look at B<EMBED> section in |
91 | various configuration options please have a look at B<EMBED> section in |
92 | this manual. If libev was configured without support for multiple event |
92 | this manual. If libev was configured without support for multiple event |
93 | loops, then all functions taking an initial argument of name C<loop> |
93 | loops, then all functions taking an initial argument of name C<loop> |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
95 | |
95 | |
96 | =head1 TIME REPRESENTATION |
96 | =head2 TIME REPRESENTATION |
97 | |
97 | |
98 | Libev represents time as a single floating point number, representing the |
98 | Libev represents time as a single floating point number, representing the |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
101 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
101 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
… | |
… | |
306 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
306 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
307 | |
307 | |
308 | This is your standard select(2) backend. Not I<completely> standard, as |
308 | This is your standard select(2) backend. Not I<completely> standard, as |
309 | libev tries to roll its own fd_set with no limits on the number of fds, |
309 | libev tries to roll its own fd_set with no limits on the number of fds, |
310 | but if that fails, expect a fairly low limit on the number of fds when |
310 | but if that fails, expect a fairly low limit on the number of fds when |
311 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
311 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
312 | the fastest backend for a low number of fds. |
312 | usually the fastest backend for a low number of (low-numbered :) fds. |
|
|
313 | |
|
|
314 | To get good performance out of this backend you need a high amount of |
|
|
315 | parallelity (most of the file descriptors should be busy). If you are |
|
|
316 | writing a server, you should C<accept ()> in a loop to accept as many |
|
|
317 | connections as possible during one iteration. You might also want to have |
|
|
318 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
|
|
319 | readyness notifications you get per iteration. |
313 | |
320 | |
314 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
321 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
315 | |
322 | |
316 | And this is your standard poll(2) backend. It's more complicated than |
323 | And this is your standard poll(2) backend. It's more complicated |
317 | select, but handles sparse fds better and has no artificial limit on the |
324 | than select, but handles sparse fds better and has no artificial |
318 | number of fds you can use (except it will slow down considerably with a |
325 | limit on the number of fds you can use (except it will slow down |
319 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
326 | considerably with a lot of inactive fds). It scales similarly to select, |
|
|
327 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
|
|
328 | performance tips. |
320 | |
329 | |
321 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
330 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
322 | |
331 | |
323 | For few fds, this backend is a bit little slower than poll and select, |
332 | For few fds, this backend is a bit little slower than poll and select, |
324 | but it scales phenomenally better. While poll and select usually scale |
333 | but it scales phenomenally better. While poll and select usually scale |
325 | like O(total_fds) where n is the total number of fds (or the highest fd), |
334 | like O(total_fds) where n is the total number of fds (or the highest fd), |
326 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
335 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
327 | of shortcomings, such as silently dropping events in some hard-to-detect |
336 | of shortcomings, such as silently dropping events in some hard-to-detect |
328 | cases and rewiring a syscall per fd change, no fork support and bad |
337 | cases and rewiring a syscall per fd change, no fork support and bad |
329 | support for dup: |
338 | support for dup. |
330 | |
339 | |
331 | While stopping, setting and starting an I/O watcher in the same iteration |
340 | While stopping, setting and starting an I/O watcher in the same iteration |
332 | will result in some caching, there is still a syscall per such incident |
341 | will result in some caching, there is still a syscall per such incident |
333 | (because the fd could point to a different file description now), so its |
342 | (because the fd could point to a different file description now), so its |
334 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
343 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
… | |
… | |
336 | |
345 | |
337 | Please note that epoll sometimes generates spurious notifications, so you |
346 | Please note that epoll sometimes generates spurious notifications, so you |
338 | need to use non-blocking I/O or other means to avoid blocking when no data |
347 | need to use non-blocking I/O or other means to avoid blocking when no data |
339 | (or space) is available. |
348 | (or space) is available. |
340 | |
349 | |
|
|
350 | Best performance from this backend is achieved by not unregistering all |
|
|
351 | watchers for a file descriptor until it has been closed, if possible, i.e. |
|
|
352 | keep at least one watcher active per fd at all times. |
|
|
353 | |
|
|
354 | While nominally embeddeble in other event loops, this feature is broken in |
|
|
355 | all kernel versions tested so far. |
|
|
356 | |
341 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
357 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
342 | |
358 | |
343 | Kqueue deserves special mention, as at the time of this writing, it |
359 | Kqueue deserves special mention, as at the time of this writing, it |
344 | was broken on I<all> BSDs (usually it doesn't work with anything but |
360 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
345 | sockets and pipes, except on Darwin, where of course it's completely |
361 | with anything but sockets and pipes, except on Darwin, where of course |
346 | useless. On NetBSD, it seems to work for all the FD types I tested, so it |
|
|
347 | is used by default there). For this reason it's not being "autodetected" |
362 | it's completely useless). For this reason it's not being "autodetected" |
348 | unless you explicitly specify it explicitly in the flags (i.e. using |
363 | unless you explicitly specify it explicitly in the flags (i.e. using |
349 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
364 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
350 | system like NetBSD. |
365 | system like NetBSD. |
351 | |
366 | |
|
|
367 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
368 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
369 | the target platform). See C<ev_embed> watchers for more info. |
|
|
370 | |
352 | It scales in the same way as the epoll backend, but the interface to the |
371 | It scales in the same way as the epoll backend, but the interface to the |
353 | kernel is more efficient (which says nothing about its actual speed, |
372 | kernel is more efficient (which says nothing about its actual speed, of |
354 | of course). While stopping, setting and starting an I/O watcher does |
373 | course). While stopping, setting and starting an I/O watcher does never |
355 | never cause an extra syscall as with epoll, it still adds up to two event |
374 | cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to |
356 | changes per incident, support for C<fork ()> is very bad and it drops fds |
375 | two event changes per incident, support for C<fork ()> is very bad and it |
357 | silently in similarly hard-to-detetc cases. |
376 | drops fds silently in similarly hard-to-detect cases. |
|
|
377 | |
|
|
378 | This backend usually performs well under most conditions. |
|
|
379 | |
|
|
380 | While nominally embeddable in other event loops, this doesn't work |
|
|
381 | everywhere, so you might need to test for this. And since it is broken |
|
|
382 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
383 | (for which it usually works), by embedding it into another event loop |
|
|
384 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
|
|
385 | sockets. |
358 | |
386 | |
359 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
387 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
360 | |
388 | |
361 | This is not implemented yet (and might never be). |
389 | This is not implemented yet (and might never be, unless you send me an |
|
|
390 | implementation). According to reports, C</dev/poll> only supports sockets |
|
|
391 | and is not embeddable, which would limit the usefulness of this backend |
|
|
392 | immensely. |
362 | |
393 | |
363 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
394 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
364 | |
395 | |
365 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
396 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
366 | it's really slow, but it still scales very well (O(active_fds)). |
397 | it's really slow, but it still scales very well (O(active_fds)). |
367 | |
398 | |
368 | Please note that solaris event ports can deliver a lot of spurious |
399 | Please note that solaris event ports can deliver a lot of spurious |
369 | notifications, so you need to use non-blocking I/O or other means to avoid |
400 | notifications, so you need to use non-blocking I/O or other means to avoid |
370 | blocking when no data (or space) is available. |
401 | blocking when no data (or space) is available. |
371 | |
402 | |
|
|
403 | While this backend scales well, it requires one system call per active |
|
|
404 | file descriptor per loop iteration. For small and medium numbers of file |
|
|
405 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
|
|
406 | might perform better. |
|
|
407 | |
372 | =item C<EVBACKEND_ALL> |
408 | =item C<EVBACKEND_ALL> |
373 | |
409 | |
374 | Try all backends (even potentially broken ones that wouldn't be tried |
410 | Try all backends (even potentially broken ones that wouldn't be tried |
375 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
411 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
376 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
412 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
|
|
413 | |
|
|
414 | It is definitely not recommended to use this flag. |
377 | |
415 | |
378 | =back |
416 | =back |
379 | |
417 | |
380 | If one or more of these are ored into the flags value, then only these |
418 | If one or more of these are ored into the flags value, then only these |
381 | backends will be tried (in the reverse order as given here). If none are |
419 | backends will be tried (in the reverse order as given here). If none are |
… | |
… | |
596 | overhead for the actual polling but can deliver many events at once. |
634 | overhead for the actual polling but can deliver many events at once. |
597 | |
635 | |
598 | By setting a higher I<io collect interval> you allow libev to spend more |
636 | By setting a higher I<io collect interval> you allow libev to spend more |
599 | time collecting I/O events, so you can handle more events per iteration, |
637 | time collecting I/O events, so you can handle more events per iteration, |
600 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
638 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
601 | C<ev_timer>) will be not affected. Setting this to a non-null bvalue will |
639 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
602 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
640 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
603 | |
641 | |
604 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
642 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
605 | to spend more time collecting timeouts, at the expense of increased |
643 | to spend more time collecting timeouts, at the expense of increased |
606 | latency (the watcher callback will be called later). C<ev_io> watchers |
644 | latency (the watcher callback will be called later). C<ev_io> watchers |
… | |
… | |
994 | optimisations to libev. |
1032 | optimisations to libev. |
995 | |
1033 | |
996 | =head3 The special problem of dup'ed file descriptors |
1034 | =head3 The special problem of dup'ed file descriptors |
997 | |
1035 | |
998 | Some backends (e.g. epoll), cannot register events for file descriptors, |
1036 | Some backends (e.g. epoll), cannot register events for file descriptors, |
999 | but only events for the underlying file descriptions. That menas when you |
1037 | but only events for the underlying file descriptions. That means when you |
1000 | have C<dup ()>'ed file descriptors and register events for them, only one |
1038 | have C<dup ()>'ed file descriptors and register events for them, only one |
1001 | file descriptor might actually receive events. |
1039 | file descriptor might actually receive events. |
1002 | |
1040 | |
1003 | There is no workaorund possible except not registering events |
1041 | There is no workaround possible except not registering events |
1004 | for potentially C<dup ()>'ed file descriptors or to resort to |
1042 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1005 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1043 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1006 | |
1044 | |
1007 | =head3 The special problem of fork |
1045 | =head3 The special problem of fork |
1008 | |
1046 | |
1009 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1047 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
… | |
… | |
1458 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1496 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1459 | to fall back to regular polling again even with inotify, but changes are |
1497 | to fall back to regular polling again even with inotify, but changes are |
1460 | usually detected immediately, and if the file exists there will be no |
1498 | usually detected immediately, and if the file exists there will be no |
1461 | polling. |
1499 | polling. |
1462 | |
1500 | |
|
|
1501 | =head3 Inotify |
|
|
1502 | |
|
|
1503 | When C<inotify (7)> support has been compiled into libev (generally only |
|
|
1504 | available on Linux) and present at runtime, it will be used to speed up |
|
|
1505 | change detection where possible. The inotify descriptor will be created lazily |
|
|
1506 | when the first C<ev_stat> watcher is being started. |
|
|
1507 | |
|
|
1508 | Inotify presense does not change the semantics of C<ev_stat> watchers |
|
|
1509 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
1510 | making regular C<stat> calls. Even in the presense of inotify support |
|
|
1511 | there are many cases where libev has to resort to regular C<stat> polling. |
|
|
1512 | |
|
|
1513 | (There is no support for kqueue, as apparently it cannot be used to |
|
|
1514 | implement this functionality, due to the requirement of having a file |
|
|
1515 | descriptor open on the object at all times). |
|
|
1516 | |
|
|
1517 | =head3 The special problem of stat time resolution |
|
|
1518 | |
|
|
1519 | The C<stat ()> syscall only supports full-second resolution portably, and |
|
|
1520 | even on systems where the resolution is higher, many filesystems still |
|
|
1521 | only support whole seconds. |
|
|
1522 | |
|
|
1523 | That means that, if the time is the only thing that changes, you might |
|
|
1524 | miss updates: on the first update, C<ev_stat> detects a change and calls |
|
|
1525 | your callback, which does something. When there is another update within |
|
|
1526 | the same second, C<ev_stat> will be unable to detect it. |
|
|
1527 | |
|
|
1528 | The solution to this is to delay acting on a change for a second (or till |
|
|
1529 | the next second boundary), using a roughly one-second delay C<ev_timer> |
|
|
1530 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
|
|
1531 | is added to work around small timing inconsistencies of some operating |
|
|
1532 | systems. |
|
|
1533 | |
1463 | =head3 Watcher-Specific Functions and Data Members |
1534 | =head3 Watcher-Specific Functions and Data Members |
1464 | |
1535 | |
1465 | =over 4 |
1536 | =over 4 |
1466 | |
1537 | |
1467 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
1538 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
… | |
… | |
1504 | =item const char *path [read-only] |
1575 | =item const char *path [read-only] |
1505 | |
1576 | |
1506 | The filesystem path that is being watched. |
1577 | The filesystem path that is being watched. |
1507 | |
1578 | |
1508 | =back |
1579 | =back |
|
|
1580 | |
|
|
1581 | =head3 Examples |
1509 | |
1582 | |
1510 | Example: Watch C</etc/passwd> for attribute changes. |
1583 | Example: Watch C</etc/passwd> for attribute changes. |
1511 | |
1584 | |
1512 | static void |
1585 | static void |
1513 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1586 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
… | |
… | |
1526 | } |
1599 | } |
1527 | |
1600 | |
1528 | ... |
1601 | ... |
1529 | ev_stat passwd; |
1602 | ev_stat passwd; |
1530 | |
1603 | |
1531 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); |
1604 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1532 | ev_stat_start (loop, &passwd); |
1605 | ev_stat_start (loop, &passwd); |
|
|
1606 | |
|
|
1607 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
1608 | miss updates (however, frequent updates will delay processing, too, so |
|
|
1609 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
1610 | C<ev_timer> callback invocation). |
|
|
1611 | |
|
|
1612 | static ev_stat passwd; |
|
|
1613 | static ev_timer timer; |
|
|
1614 | |
|
|
1615 | static void |
|
|
1616 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1617 | { |
|
|
1618 | ev_timer_stop (EV_A_ w); |
|
|
1619 | |
|
|
1620 | /* now it's one second after the most recent passwd change */ |
|
|
1621 | } |
|
|
1622 | |
|
|
1623 | static void |
|
|
1624 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
1625 | { |
|
|
1626 | /* reset the one-second timer */ |
|
|
1627 | ev_timer_again (EV_A_ &timer); |
|
|
1628 | } |
|
|
1629 | |
|
|
1630 | ... |
|
|
1631 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
1632 | ev_stat_start (loop, &passwd); |
|
|
1633 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1533 | |
1634 | |
1534 | |
1635 | |
1535 | =head2 C<ev_idle> - when you've got nothing better to do... |
1636 | =head2 C<ev_idle> - when you've got nothing better to do... |
1536 | |
1637 | |
1537 | Idle watchers trigger events when no other events of the same or higher |
1638 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1623 | |
1724 | |
1624 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1725 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1625 | priority, to ensure that they are being run before any other watchers |
1726 | priority, to ensure that they are being run before any other watchers |
1626 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1727 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1627 | too) should not activate ("feed") events into libev. While libev fully |
1728 | too) should not activate ("feed") events into libev. While libev fully |
1628 | supports this, they will be called before other C<ev_check> watchers did |
1729 | supports this, they will be called before other C<ev_check> watchers |
1629 | their job. As C<ev_check> watchers are often used to embed other event |
1730 | did their job. As C<ev_check> watchers are often used to embed other |
1630 | loops those other event loops might be in an unusable state until their |
1731 | (non-libev) event loops those other event loops might be in an unusable |
1631 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1732 | state until their C<ev_check> watcher ran (always remind yourself to |
1632 | others). |
1733 | coexist peacefully with others). |
1633 | |
1734 | |
1634 | =head3 Watcher-Specific Functions and Data Members |
1735 | =head3 Watcher-Specific Functions and Data Members |
1635 | |
1736 | |
1636 | =over 4 |
1737 | =over 4 |
1637 | |
1738 | |
… | |
… | |
1776 | =head2 C<ev_embed> - when one backend isn't enough... |
1877 | =head2 C<ev_embed> - when one backend isn't enough... |
1777 | |
1878 | |
1778 | This is a rather advanced watcher type that lets you embed one event loop |
1879 | This is a rather advanced watcher type that lets you embed one event loop |
1779 | into another (currently only C<ev_io> events are supported in the embedded |
1880 | into another (currently only C<ev_io> events are supported in the embedded |
1780 | loop, other types of watchers might be handled in a delayed or incorrect |
1881 | loop, other types of watchers might be handled in a delayed or incorrect |
1781 | fashion and must not be used). (See portability notes, below). |
1882 | fashion and must not be used). |
1782 | |
1883 | |
1783 | There are primarily two reasons you would want that: work around bugs and |
1884 | There are primarily two reasons you would want that: work around bugs and |
1784 | prioritise I/O. |
1885 | prioritise I/O. |
1785 | |
1886 | |
1786 | As an example for a bug workaround, the kqueue backend might only support |
1887 | As an example for a bug workaround, the kqueue backend might only support |
… | |
… | |
1841 | ev_embed_start (loop_hi, &embed); |
1942 | ev_embed_start (loop_hi, &embed); |
1842 | } |
1943 | } |
1843 | else |
1944 | else |
1844 | loop_lo = loop_hi; |
1945 | loop_lo = loop_hi; |
1845 | |
1946 | |
1846 | =head2 Portability notes |
|
|
1847 | |
|
|
1848 | Kqueue is nominally embeddable, but this is broken on all BSDs that I |
|
|
1849 | tried, in various ways. Usually the embedded event loop will simply never |
|
|
1850 | receive events, sometimes it will only trigger a few times, sometimes in a |
|
|
1851 | loop. Epoll is also nominally embeddable, but many Linux kernel versions |
|
|
1852 | will always eport the epoll fd as ready, even when no events are pending. |
|
|
1853 | |
|
|
1854 | While libev allows embedding these backends (they are contained in |
|
|
1855 | C<ev_embeddable_backends ()>), take extreme care that it will actually |
|
|
1856 | work. |
|
|
1857 | |
|
|
1858 | When in doubt, create a dynamic event loop forced to use sockets (this |
|
|
1859 | usually works) and possibly another thread and a pipe or so to report to |
|
|
1860 | your main event loop. |
|
|
1861 | |
|
|
1862 | =head3 Watcher-Specific Functions and Data Members |
1947 | =head3 Watcher-Specific Functions and Data Members |
1863 | |
1948 | |
1864 | =over 4 |
1949 | =over 4 |
1865 | |
1950 | |
1866 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
1951 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
… | |
… | |
2504 | than enough. If you need to manage thousands of children you might want to |
2589 | than enough. If you need to manage thousands of children you might want to |
2505 | increase this value (I<must> be a power of two). |
2590 | increase this value (I<must> be a power of two). |
2506 | |
2591 | |
2507 | =item EV_INOTIFY_HASHSIZE |
2592 | =item EV_INOTIFY_HASHSIZE |
2508 | |
2593 | |
2509 | C<ev_staz> watchers use a small hash table to distribute workload by |
2594 | C<ev_stat> watchers use a small hash table to distribute workload by |
2510 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2595 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2511 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2596 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2512 | watchers you might want to increase this value (I<must> be a power of |
2597 | watchers you might want to increase this value (I<must> be a power of |
2513 | two). |
2598 | two). |
2514 | |
2599 | |
… | |
… | |
2610 | |
2695 | |
2611 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2696 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2612 | |
2697 | |
2613 | This means that, when you have a watcher that triggers in one hour and |
2698 | This means that, when you have a watcher that triggers in one hour and |
2614 | there are 100 watchers that would trigger before that then inserting will |
2699 | there are 100 watchers that would trigger before that then inserting will |
2615 | have to skip those 100 watchers. |
2700 | have to skip roughly seven (C<ld 100>) of these watchers. |
2616 | |
2701 | |
2617 | =item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) |
2702 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2618 | |
2703 | |
2619 | That means that for changing a timer costs less than removing/adding them |
2704 | That means that changing a timer costs less than removing/adding them |
2620 | as only the relative motion in the event queue has to be paid for. |
2705 | as only the relative motion in the event queue has to be paid for. |
2621 | |
2706 | |
2622 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2707 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2623 | |
2708 | |
2624 | These just add the watcher into an array or at the head of a list. |
2709 | These just add the watcher into an array or at the head of a list. |
|
|
2710 | |
2625 | =item Stopping check/prepare/idle watchers: O(1) |
2711 | =item Stopping check/prepare/idle watchers: O(1) |
2626 | |
2712 | |
2627 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2713 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2628 | |
2714 | |
2629 | These watchers are stored in lists then need to be walked to find the |
2715 | These watchers are stored in lists then need to be walked to find the |
2630 | correct watcher to remove. The lists are usually short (you don't usually |
2716 | correct watcher to remove. The lists are usually short (you don't usually |
2631 | have many watchers waiting for the same fd or signal). |
2717 | have many watchers waiting for the same fd or signal). |
2632 | |
2718 | |
2633 | =item Finding the next timer per loop iteration: O(1) |
2719 | =item Finding the next timer in each loop iteration: O(1) |
|
|
2720 | |
|
|
2721 | By virtue of using a binary heap, the next timer is always found at the |
|
|
2722 | beginning of the storage array. |
2634 | |
2723 | |
2635 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2724 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2636 | |
2725 | |
2637 | A change means an I/O watcher gets started or stopped, which requires |
2726 | A change means an I/O watcher gets started or stopped, which requires |
2638 | libev to recalculate its status (and possibly tell the kernel). |
2727 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
2728 | on backend and wether C<ev_io_set> was used). |
2639 | |
2729 | |
2640 | =item Activating one watcher: O(1) |
2730 | =item Activating one watcher (putting it into the pending state): O(1) |
2641 | |
2731 | |
2642 | =item Priority handling: O(number_of_priorities) |
2732 | =item Priority handling: O(number_of_priorities) |
2643 | |
2733 | |
2644 | Priorities are implemented by allocating some space for each |
2734 | Priorities are implemented by allocating some space for each |
2645 | priority. When doing priority-based operations, libev usually has to |
2735 | priority. When doing priority-based operations, libev usually has to |
2646 | linearly search all the priorities. |
2736 | linearly search all the priorities, but starting/stopping and activating |
|
|
2737 | watchers becomes O(1) w.r.t. prioritiy handling. |
2647 | |
2738 | |
2648 | =back |
2739 | =back |
2649 | |
2740 | |
2650 | |
2741 | |
2651 | =head1 AUTHOR |
2742 | =head1 AUTHOR |